feat: implement photo albums (media groups) and persist account selection

Group photos with shared media_album_id into single album bubbles with
grid layout (up to 3x cols). Album navigation treats grouped photos as
one unit (j/k skip entire album). Persist selected account to
accounts.toml so it survives app restart.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/tdlib/message_converter.rs

@@ -76,7 +76,8 @@ pub fn convert_message(
         .text(content)
         .entities(entities)
         .date(message.date)
-        .edit_date(message.edit_date);
+        .edit_date(message.edit_date)
+        .media_album_id(message.media_album_id);
 
     // Применяем флаги
     if message.is_outgoing {